You can manually create a new file by editing one and placing it in '/etc/yum.repos.d/', however that's usually not necessary.
You have already added a repository, Livna from your yum output. The way that repositories like Livna are added is by installing an rpm that has the necessary configuration. For example:
rpm -uvh http://ftp.freshrpms.net/pub/freshrpms/fedora/linux/6/freshrpms-release/freshrpms-release-1.1-1.fc.noarch.rpm
The above command will add the FreshRPMs repository. Most repositories will have a "release" file that you can install this way. The instructions for adding a repository are usually on the home page for the repository (along with a pointer to the release file).
Be aware that adding multiple repositories can lead to conflicts, and sometimes non-working software.